Le 19/07/2022 à 12:24, David Laight a écrit :
From: Christophe JAILLET
Sent: 19 July 2022 11:02
'node_map_lock' is a spinlock only used to protect calls to set_bit(),
clear_bit() and test_bit().
{set|clear}_bit() are already atomic and don't need this extra spinlock.
test_bit() only reads the bitmap for a given bit.
Remove this useless spinlock.
It looks to me like the calling code is racy
unless there is another lock in the callers.
The call chains are:
ocfs2_recover_orphans()
ocfs2_mark_recovering_orphan_dir()
spin_lock(&osb->osb_lock); <-- osb_lock spinlock
ocfs2_node_map_set_bit() <-- uses node_map_lock
...
spin_unlock(&osb->osb_lock);
...
ocfs2_clear_recovering_orphan_dir()
ocfs2_node_map_clear_bit() <-- uses node_map_lock
osb_lock is NOT taken
ocfs2_check_orphan_recovery_state()
spin_lock(&osb->osb_lock); <-- osb_lock spinlock
...
ocfs2_node_map_test_bit() <-- uses node_map_lock
...
spin_unlock(&osb->osb_lock);
So the code looks already protected by the 'osb_lock' spinlock, but I
don't know this code and ocfs2_mark_recovering_orphan_dir() looks tricky
to me. (so some other eyes are much welcome)
While map->map is protected, the result of test_bit()
is stale - so can't be used for much.
Anyway, should there be a locking issue, it is there with or without my
patch, right?
CJ
David
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
test_bit() is NOT documented as an atomic function. However, I can't see
how it could return a wrong result here.
So review with care. There is maybe something I don't think about that is
lurking here.
---
fs/ocfs2/heartbeat.c | 11 ++++-------
fs/ocfs2/ocfs2.h | 2 --
2 files changed, 4 insertions(+), 9 deletions(-)
diff --git a/fs/ocfs2/heartbeat.c b/fs/ocfs2/heartbeat.c
index 1d72e0788943..4863ad35c242 100644
--- a/fs/ocfs2/heartbeat.c
+++ b/fs/ocfs2/heartbeat.c
@@ -35,7 +35,6 @@ static void ocfs2_node_map_init(struct ocfs2_node_map *map)
void ocfs2_init_node_maps(struct ocfs2_super *osb)
{
- spin_lock_init(&osb->node_map_lock);
ocfs2_node_map_init(&osb->osb_recovering_orphan_dirs);
}
@@ -67,9 +66,8 @@ void ocfs2_node_map_set_bit(struct ocfs2_super *osb,
if (bit==-1)
return;
BUG_ON(bit >= map->num_nodes);
- spin_lock(&osb->node_map_lock);
+
set_bit(bit, map->map);
- spin_unlock(&osb->node_map_lock);
}
void ocfs2_node_map_clear_bit(struct ocfs2_super *osb,
@@ -79,9 +77,8 @@ void ocfs2_node_map_clear_bit(struct ocfs2_super *osb,
if (bit==-1)
return;
BUG_ON(bit >= map->num_nodes);
- spin_lock(&osb->node_map_lock);
+
clear_bit(bit, map->map);
- spin_unlock(&osb->node_map_lock);
}
int ocfs2_node_map_test_bit(struct ocfs2_super *osb,
@@ -89,13 +86,13 @@ int ocfs2_node_map_test_bit(struct ocfs2_super *osb,
int bit)
{
int ret;
+
if (bit >= map->num_nodes) {
mlog(ML_ERROR, "bit=%d map->num_nodes=%d\n", bit, map->num_nodes);
BUG();
}
- spin_lock(&osb->node_map_lock);
+
ret = test_bit(bit, map->map);
- spin_unlock(&osb->node_map_lock);
return ret;
}
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 740b64238312..1df193b97c30 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -302,8 +302,6 @@ struct ocfs2_super
u32 *slot_recovery_generations;
- spinlock_t node_map_lock;
-
u64 root_blkno;
u64 system_dir_blkno;
u64 bitmap_blkno;
--
2.34.1
-
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